Nanoscience is the science of materials between approximately 1 and 100 nm in size; more importantly, at such sizes novel and size dependent behaviors reveal themselves. For instance, much work has been performed with nano-gold, where, at larger size scales, it is chemically inert. However, as size goes below about 10 nm, gold nanoparticles (NPs) become powerful catalysts and can be used, for example, in composites for environmental remediation. In addition, the optical properties of NPs change radically within the nano-range, because of interactions between incident light and surface electrons on the NP. Such behavior reveals itself in color changes as a function of size and is providing technology such as optically-based sensors.
Due to these novel properties, nanotechnology underpins a large and exponentially growing area of industry with global research and development investment of thousands of millions of dollars per year and global markets estimated in the trillions of dollars in the next few years. Current estimates suggest that there are many hundreds of NM-containing products on the market and this number is increasing linearly year on year. Currently consumer products are mainly at the low technology end of the sector e.g. carbon nanotubes used as structural materials, C60 fullerenes, titania and zinc oxide NPs used in cosmetics and sunscreens, Ag used as a bacteriocide in fabrics and elsewhere.
Given the large and increasing usage, environmental exposure is already occurring and likely to increase and models have been developed which have estimated exposure for a range of nanoparticles including nano-silver, nano-titania and carbon nanotubes, although data for model validation and parameterization is largely missing. In addition, bioaccumulation, toxicity or potential toxicity of a number of these materials have been established, but the mechanism of action or the important chemical species contributing to bioaccumulation and toxicity has not been established. In particular for metals and metal oxides the relative importance of the particle and ion phases in biouptake is variable for different nanoparticles but not quantitatively understood. Given the hazard and exposure, there is likely to be a risk to the environment and to human health, although this is very poorly characterized as yet including in terms of the bioaccumulated species. The long term sustainability of this highly beneficial industry requires greater understanding of the risks, minimization of these risks and that these risks are seen to be mitigated. In short, the impacts of NP dissolution on bioaccumulation and toxicity (along with fate and behavior) remain highly uncertain.